1. Field of the Invention
The present invention relates generally to GPS receiving devices and more particularly to a mobile accessory-type GPS receiver.
2. Description of the Related Art
The GPS (Global Positioning System) comprises 24 satellites orbiting 12,000 miles above the Earth, each one making two complete rotations per day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites “visible” in the sky. GPS receivers are designed to locate four or more of these satellites, figure out the relative distance to each satellite, and use this information to deduce its own location.
GPS makes it possible for users equipped with ground receivers to pinpoint their own geographic location with ever-increasing accuracy. In general, the location accuracy may be anywhere from 10 to 100 meters for most run-of the-mill GPS equipment. Accuracy may be pinpointed to within one (1) meter with military-approved equipment.
Mobile GPS receivers have presently become sufficiently low-cost and portable to attract a relatively large pool of users thus becoming common consumer products. In addition to their outdoor use, such as during hiking, cross-country skiing, ballooning, flying, and sailing, mobile GPS receivers are being used in vehicles to correlate the driver's location with traffic and weather information.
Mobile GPS receivers are generally of the cradle or accessory type. FIG. 1 generally illustrates a cradle-type GPS receiver 10 which may be used in vehicles. With this type of receiver, a GPS antenna may be affixed at an arbitrary position inside the vehicle so as to implement an optimal GPS reception environment.
FIG. 2 generally depicts an accessory-type GPS receiver 12 which may be carried around by an individual user. With this type of receiver, an active GPS antenna (not shown) is integrally coupled to the GPS receiver 12. The accessory-type GPS receiver 12 may be operatively coupled to a mobile terminal 14 via a data link cable 16. The accessory-type GPS receiver 12 may also be portable enough to be worn like a necklace or stored in a shirt pocket or the like.
In contrast, the cradle-type GPS receiver 10 cannot be carried around like an accessory-type GPS receiver. If the user desires to adapt the GPS receiver 10 for additional functionality, a new special cradle would have to be used which would add to the cost of usage.
The accessory-type GPS receiver 12, however, also carries some inherent disadvantages. For example, the data link cable 16 may not be used to power the accessory-type GPS receiver 12 and charge the battery of the mobile terminal 14 at the same time. Also, wearing the accessory-type GPS receiver 12 around one's neck or in one's shirt pocket while hand-carrying the mobile terminal 14, which is coupled to the accessory-type GPS receiver 12 may be somewhat cumbersome for some mobile GPS receiver users.